[!IMPORTANT]
The default branch of this repository is 5-stable
(Sisimai 5) since 2nd February 2024.
If you want to clone the old version, see the 4-stable[^1]
branch instead. We have moved away from using both the main and master branches in our development process.
[^1]: Specify -b 4-stable when you clone Sisimai 4 for example, git clone -b 4-stable https://github.com/sisimai/p5-sisimai.git
[!CAUTION] Sisimai versions 4.25.14p11 and earlier contain a regular expression vulnerability ReDoS: CVE-2022-4891. If you are using one of these versions, please upgrade to v4.25.14p12 or later.
[!WARNING]
Sisimai 5 requires Perl 5.26 or later. Check the version of Perl in your system before installing/upgrading
by perl -v command.
[!NOTE] Sisimai is a Perl module or Ruby Gem, but it can be used in any environment where JSON can be read, such as PHP, Python, Go, and Rust. By obtaining the analysis results, it is very useful for understanding the bounce occurrence status.
- 🇯🇵README-JA
- What is Sisimai
- Setting Up Sisimai
- Usage
- Differences between Sisimai 4 and Sisimai 5
- Contributing
- Other Information
- Author
- Copyright
- License
What is Sisimai
Sisimai (pronounced /ɕi.ɕi.ma.i/) is a library that decodes complex and diverse bounce emails and outputs the results of the delivery failure, such as the reason for the bounce and the recipient email address, in structured data. It is also possible to output in JSON format.

The key features of Sisimai
- Decode email bounces to structured data
- Sisimai provides detailed insights into bounce emails by extracting 27 key data points.[^2]
- Essential information:
timestamp,origin - Sender information:
addresser,senderdomain, - Recipient information:
recipient,destination,alias - Delivery information:
action,replycode,deliverystatus,command - Bounce details:
reason,diagnosticcode,diagnostictype,feedbacktype,feedbackid,hardbounce - Message details:
subject,messageid,listid, - Additional information:
decodedby,timezoneoffset,lhost,rhost,token,catch,toxic
- Essential information:
- Output formats
- Perl (Hash, Array)
- JSON (by using
JSONmodule) - YAML (
YAMLmodule orYAML::Syckmodule required)
- Sisimai provides detailed insights into bounce emails by extracting 27 key data points.[^2]
- Easy to Install, Use.
cpan,cpanm, orcpmgit clone & make
- High Precision of Analysis
- Support 60 MTAs/MDAs/ESPs
- Support Feedback Loop Message(ARF)
- Can detect 34 bounce reasons
[^2]: The callback function allows you to add your own data under the catch accessor.
Command line demo
The following screen shows a demonstration of dump method of Sisimai 5 at the command line using
Perl(p5-sisimai) and jq command.

Setting Up Sisimai
System requirements
More details about system requirements are available at Sisimai | Getting Started page.
Install
From CPAN
$ cpanm --sudo Sisimai
--> Working on Sisimai
Fetching http://www.cpan.org/authors/id/A/AK/AKXLIX/Sisimai-5.6.0.tar.gz ... OK
...
1 distribution installed
$ perldoc -l Sisimai
/usr/local/lib/perl5/site_perl/5.30.0/Sisimai.pm
From GitHub
[!WARNING]
Sisimai 5 requires Perl 5.26 or later. Check the version of Perl in your system before installing/upgrading
by perl -v command.
$ perl -v
This is perl 5, version 30, subversion 0 (v5.30.0) built for darwin-2level
Copyright 1987-2019, Larry Wall
...
$ cd /usr/local/src
$ git clone https://github.com/sisimai/p5-sisimai.git
$ cd ./p5-sisimai
$ make install-from-local
./cpanm --sudo . || ( make cpm && ./cpm install --sudo -v . )
--> Working on .
Configuring Sisimai-v5.6.0 ... OK
Building and testing Sisimai-v5.6.0 ... Password: <sudo password here>
OK
Successfully installed Sisimai-v5.6.0
1 distribution installed
$ perl -MSisimai -lE 'print Sisimai->version'
5.6.0
Usage
Basic usage
Sisimai->rise() method provides the feature for getting decoded data as Perl Hash reference from
bounced email messages as the following. Beginning with v4.25.6, new accessor origin which keeps
the path to email file as a data source is available.
#! /usr/bin/env perl
use Sisimai;
my $v = Sisimai->rise('/path/to/mbox'); # or path to Maildir/
# In v4.23.0, the rise() and dump() methods of the Sisimai class can now read the entire bounce
# email as a string, in addition to the PATH to the email file or mailbox.
use IO::File;
my $r = '';
my $f = IO::File->new('/path/to/mbox'); # or path to Maildir/
{ local $/ = undef; $r = <$f>; $f->close }
my $v = Sisimai->rise(\$r);
# If you also need analysis results that are "delivered" (successfully delivered), please specify
# the "delivered" option to the rise() method as shown below.
my $v = Sisimai->rise('/path/to/mbox', 'delivered' => 1);
# From v5.0.0, Sisimai no longer returns analysis results with a bounce reason of "vacation" by
# default. If you also need analysis results that show a "vacation" reason, please specify the
# "vacation" option to the rise() method as shown in the following code.
my $v = Sisimai->rise('/path/to/mbox', 'vacation' => 1);
if( defined $v ) {
for my $e ( @$v ) {
print ref $e; # Sisimai::Fact
print ref $e->recipient; # Sisimai::Address
print ref $e->timestamp; # Sisimai::Time
print $e->addresser->address; # "michitsuna@example.org" # From
print $e->recipient->address; # "kijitora@example.jp" # To
print $e->recipient->host; # "example.jp"
print $e->deliverystatus; # "5.1.1"
print $e->replycode; # "550"
print $e->reason; # "userunknown"
print $e->origin; # "/var/spool/bounce/new/1740074341.eml"
print $e->hardbounce; # 1
my $h = $e->damn(); # Convert to HASH reference
my $j = $e->dump('json'); # Convert to JSON string
print $e->dump('json'); # JSON formatted bounce data
}
}
Convert to JSON
Sisimai->dump() method provides the feature for getting decoded data as JSON string from bounced
email messages like the following code:
#! /usr/bin/env perl
use Sisimai;
# Get JSON string from path of a mailbox or a Maildir/
my $j = Sisimai->dump('/path/to/mbox'); # or path to Maildir/
# dump() is added in v4.1.27
print $j; # decoded data as JSON
# dump() method also accepts "delivered" and "vacation" option like the following code:
my $j = Sisimai->dump('/path/to/mbox', 'delivered' => 1, 'vacation' => 1);
Callback feature
c___ (c and three _s, looks like a fishhook) argument of Sisimai->rise and Sisimai->dump
is an array reference and is a parameter to receive code references for callback feature. The first
element of c___ argument is called at Sisimai::Message->sift for dealing email headers and
entire message body. The second element of c___ argument is called at the end of each email file
processing. The result generated by the callback method is accessible via Sisimai::Fact->catch.
[0] For email headers and the body
Callback method set in the first element of c___ is called at Sisimai::Message->sift().
#! /usr/bin/env perl
use Sisimai;
my $code = sub {
my $args = shift; # (*Hash)
my $head = $args->{'headers'}; # (*Hash) Email headers
my $body = $args->{'message'}; # (String) Message body
my $adds = { 'x-mailer' => '', 'queue-id' => '' };
if( $body =~ m/^X-Postfix-Queue-ID:\s*(.+)$/m ) {
$adds->{'queue-id'} = $1;
}
$adds->{'x-mailer'} = $head->{'x-mailer'} || '';
return $adds;
};
my $data = Sisimai->rise('/path/to/mbox', 'c___' => [$code, undef]);
my $json = Sisimai->dump('/path/to/mbox', 'c___' => [$code, undef]);
print $data->[0]->catch->{'x-mailer'}; # "Apple Mail (2.1283)"
print $data->[0]->catch->{'queue-id'}; # "43f4KX6WR7z1xcMG"
[1] For each email file
Callback method set in the second element of c___ is called at Sisimai->rise() method for
dealing each email file.
my $path = '/path/to/maildir';
my $code = sub {
my $args = shift; # (*Hash)
my $kind = $args->{'kind'}; # (String) Sisimai::Mail->kind
my $mail = $args->{'mail'}; # (*String) Entire email message
my $path = $args->{'path'}; # (String) Sisimai::Mail->path
my $fact = $args->{'fact'}; # (*Array) List of Sisimai::Fact
for my $e ( @$fact ) {
# Store custom information in the "catch" accessor.
$e->{'catch'} ||= {};
$e->{'catch'}->{'size'} = length $$mail;
$e->{'catch'}->{'kind'} = ucfirst $kind;
if( $$mail =~ /^Return-Path: (.+)$/m ) {
# Return-Path: <MAILER-DAEMON>
$e->{'catch'}->{'return-path'} = $1;
}
# Save the original email with an additional "X-Sisimai-Parsed:" header to a different PATH.
my $a = sprintf("X-Sisimai-Parsed: %d\n", scalar @$fact);
my $p = sprintf("/path/to/another/directory/sisimai-%s.eml", $e->token);
my $f = IO::File->new($p, 'w');
my $v = $$mail; $v =~ s/^(From:.+)$/$a$1/m;
print $f $v; $f->close;
}
# Remove the email file in Maildir/ after decoding
unlink $path if $kind eq 'maildir';
# Need to not return a value
};
my $list = Sisimai->rise($path, 'c___' => [undef, $code]);
print $list->[0]->{'catch'}->{'size'}; # 2202
print $list->[0]->{'catch'}->{'kind'}; # "Maildir"
print $list->[0]->{'catch'}->{'return-path'}; # "<MAILER-DAEMON>"
More information about the callback feature is available at Sisimai | How To Parse - Callback Page.
One-Liner
Beginning with Sisimai 4.1.27, Sisimai->dump() method is available and you can get decoded data
as JSON using the method.
$ perl -MSisimai -lE 'print Sisimai->dump(shift)' /path/to/mbox
Output example

[
{
"destination": "google.example.com",
"lhost": "gmail-smtp-in.l.google.com",
"hardbounce": 0,
"reason": "authfailure",
"catch": null,
"addresser": "michitsuna@example.jp",
"alias": "nekochan@example.co.jp",
"decodedby": "Postfix",
"command": "DATA",
"senderdomain": "example.jp",
"listid": "",
"action": "failed",
"feedbacktype": "",
"messageid": "hwK7pzjzJtz0RF9Y@relay3.example.com",
"origin": "./gmail-5.7.26.eml",
"recipient": "kijitora@google.example.com",
"rhost": "gmail-smtp-in.l.google.com",
"subject": "Nyaan",
"timezoneoffset": "+0900",
"replycode": 550,
"token": "84656774898baa90660be3e12fe0526e108d4473",
"toxic": false,
"diagnostictype": "SMTP",
"timestamp": 1650119685,
"diagnosticcode": "host gmail-smtp-in.l.google.com[64.233.187.27] said: This mail has been blocked because the sender is unauthenticated. Gmail requires all senders to authenticate with either SPF or DKIM. Authentication results: DKIM = did not pass SPF [relay3.example.com] with ip: [192.0.2.22] = did not pass For instructions on setting up authentication, go to https://support.google.com/mail/answer/81126#authentication c2-202200202020202020222222cat.127 - gsmtp (in reply to end of DATA command)",
"deliverystatus": "5.7.26"
}
]
Differences between Sisimai 4 and Sisimai 5
The following table show the differences between Sisimai 4.25.16p1 and Sisimai 5. More information about differences are available at Sisimai | Differences page.
Features
Beginning with v5.0.0, Sisimai requires Perl 5.26.0 or later.
| Features | Sisimai 4 | Sisimai 5 | |------------------------------------------------------|--------------------|---------------------| | System requirements (Perl) | 5.10 - | 5.26 - | | Callback feature for the original email file | N/A | Available[^3] | | The number of MTA/ESP modules | 68 | 60 | | The number of detectable bounce reasons | 29 | 34 | | Dependencies (Except core modules of Perl) | 2 modules | 2 modules | | Source lines of code | 10,800 lines | 9,750 lines | | The number of tests in t/, xt/ directory | 270,000 tests | 340,000 tests | | The number of bounce emails decoded per second[^4] | 750 emails | 750 emails | | License | 2 Clause BSD | 2 Caluse BSD | | Commercial support | Available | Available |
[^3]: The 2nd argument of c___ parameter at Sisimai->rise method
[^4]: macOS Monterey/1.6GHz Dual-Core Intel Core i5/16GB-RAM/Perl 5.30
Decoding Method
Some decoding method names, class names, parameter names have been changed at Sisimai 5. The details of the decoded data are available at LIBSISIMAI.ORG/EN/DATA
| Decoding Method | Sisimai 4 | Sisimai 5 |
|------------------------------------------------------|--------------------|---------------------|
| Decoding method name | Sisimai->make | Sisimai->rise |
| Dumping method name | Sisimai->dump | Sisimai->dump |
| Class name of decoded object | Sisimai::Data | Sisimai::Fact |
| Parameter name of the callback | hook | c___[^5] |
| Method name for checking the hard/soft bounce | softbounce | hardbounce |
| Decode a vacation message by default | Yes | No |
| Sisimai::Message returns an object | Yes | No |
| MIME decoding class | Sisimai::MIME | Sisimai::RFC2045 |
| Decoding transcript of SMTP session | No | Yes[^6] |
[^5]: c___ looks like a fishhook
[^6]: Sisimai::SMTP::Transcript->rise Method provides the feature
MTA/ESP Module Names
Three ESP module names have been changed at Sisimai 5. The list of the all MTA/ESP modules is available at LIBSISIMAI.ORG/EN/ENGINE
| Sisimai:: | Sisimai 4 | Sisimai 5 |
|-------------------------------------------------|-------------------------|---------------------|
| Apple iCloud Mail (added at v5.1.0) | None | Rhost::Apple |
| Microsoft Exchange Online | Rhost::ExchangeOnline | Rhost::Microsoft |
| Google Workspace | Rhost::GoogleApps | Rhost::Google |
| Tencent | Rhost::TencentQQ | Rhost::Tencent |
| Yahoo Mail (added at v5.1.0) | None | Rhost::YahooInc |
| Zoho (added at v5.5.0) | None | Rhost::Zoho |
| DragonFly Mail Agent (added at v5.1.0) | None | Lhost::DragonFly |
| Mimecast (added at v5.5.0) | None | Lhost::Mimecast |
Bounce Reasons
Five bounce reasons have been added at Sisimai 5. The list of the all bounce reasons sisimai can detect is available at LIBSISIMAI.ORG/EN/REASON
| Rejected due to | Sisimai 4 | Sisimai 5 |
|------------------------------------------------------|--------------------|---------------------|
| sender domain authentication(SPF,DKIM,DMARC) | SecurityError | AuthFailure |
| low/bad reputation of the sender hostname/IP addr. | Blocked | BadReputation |
| missing PTR/having invalid PTR | Blocked | RequirePTR |
| non-compliance with RFC[^7] | SecurityError | NotCompliantRFC |
| STARTTLS-related errors (added at v5.2.0) | SecurityError | FailedSTARTTLS |
| exceeding a rate limit or sending too fast | SecurityError | RateLimited |
| too many concurrency connections or recipients | TooManyConn | RateLimited |
| Email size is too large for the remote host | ExceedLimit | EmailTooLarge |
| Email size is too large for the remote host | MesgTooBig | EmailTooLarge |
| Recipient in the suppression list (added at v5.2.0) | OnHold | Suppressed |
[^7]: RFC5322 and related RFCs
Contributing
Bug report
Please use the issue tracker to report any bugs.
Emails could not be decoded
Bounce mails which could not be decoded by Sisimai are saved in the repository set-of-emails/to-be-debugged-because/sisimai-cannot-parse-yet. If you have found any bounce email cannot be decoded using Sisimai, please add the email into the directory and send Pull-Request to this repository.
Other Information
Related sites
- @libsisimai | Sisimai on Twitter (@libsisimai)
- LIBSISIMAI.ORG | SISIMAI | MAIL ANALYZING INTERFACE | DECODING BOUNCES, BETTER AND FASTER.
- Facebook Page | facebook.com/libsisimai
- GitHub | github.com/sisimai/p5-sisimai
- CPAN | Sisimai - Mail Analyzing Interface for bounce mails. - metacpan.org
- CPAN Testers Reports | CPAN Testers Reports: Reports for Sisimai
- Ruby verson | Ruby version of Sisimai
- Go verson | Go version of Sisimai
- Fixtures | set-of-emails - Sample emails for "make test"
See also
- README-JA.md - README.md in Japanese(🇯🇵)
- RFC3463 - Enhanced Mail System Status Codes
- RFC3464 - An Extensible Message Format for Delivery Status Notifications
- RFC3834 - Recommendations for Automatic Responses to Electronic Mail
- RFC5321 - Simple Mail Transfer Protocol
- RFC5322 - Internet Message Format
Author
Copyright
Copyright (C) 2014-2026 azumakuniyuki, All Rights Reserved.
License
This software is distributed under The BSD 2-Clause License.